1. Field of the Invention
The present invention relates to an ink-jet printing head using inexpensive glass or plastic plates in which nozzles and ink flow channels are readily formed and which are fit for mass production.
2. Description of Related Art
A method for recording characters on a recording medium such as paper by sending out jets of ink through very small nozzles to make the ink stick thereto is known as an ink-jet recording method and on-demand type ink-jet recording heads are those based on the method above. The ink-jet recording head of this type (hereinafter called the "recording head") roughly comprises, as shown in a top view of FIG. 3 to better illustrate the groove side of a cavity plate and a sectional view of FIG. 4, a cavity plate 11, an oscillating plate 19, and piezoelectric elements 20 as electromechanical transducers each laid, on the outside face of the oscillating plate 19, opposite via conductive films to ink pressurizing chambers 15. When the cavity plate 11 ie combined with the oscillating plate 19, ink-jet nozzles 12, jet flow channels 13, ink pressurizing chambers 15, ink supply lines 16, filter flow channels 18, and an ink reservoir 17 for common use are formed as corresponding undulations have been formed by etching, machining or the like in the cavity plate 11 made of silicon, glass or metal. In this structure, the oscillating plate 19 is displaced toward the inside of the ink pressurizing chamber 15 so as to sharply reduce the capacity of the ink pressurizing chamber 15 when voltage as an electric signal is applied to the piezoelectric element 20. As a result, a quantity of ink equivalent to the reduced capacity of the ink pressurizing chamber 15 is jetted out of the nozzle 12 and the ink drops produced thereby are made to stick to opposite recording paper, so that characters are printed thereon.
In the case of a conventional ink-jet recording head of the sort mentioned above, an electrostatic bonding technique is applied to bonding the cavity plate 11 and the oscillating plate 19 together when the former and the latter are a silicon wafer and a glass plate, respectively. When a plastic cavity plate 11 is used for reducing material cost, making it easy to machine fine grooves and thus increasing mass producibility, bonding adhesives and thermal fusion bonding by heat-fusing the plastics itself are employed for bonding purposes. However, there are drawbacks common to the prior art in that the durability of the joint is inferior and that the flow channel shape is not kept accurate and is therefore slightly ruined; consequently, there has developed a demand for reliable bonding techniques. In view of improving durability and rigidity, it is put under technological scrutiny to use engineering plastics such as polyetherimide, polysulfone, polyetherketone, polyethersulfone and the like for such cavity and oscillating plates. Since these materials are generally difficult to join by means of bonding adhesives, a thermal fusion bonding method is being studied. The thermal fusion bonding method is advantageous in that bonding reliability is extremely high because no adhesive interface with a different material such as a bonding adhesive exists. Notwithstanding, there also arises the problem of thermal deformation of very small ink flow channels formed in the surface of the cavity plate due to the heat added to those plastics.